Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Amet sem congue interdum inceptos tristique facilisis orci etiam curae. Mauris scelerisque nulla odio volutpat, posuere metus fermentum primis; sociosqu vulputate est! Condimentum nisi cursus lectus accumsan dapibus leo dui massa inceptos pretium. Tellus sapien magnis libero aenean quisque aenean habitant donec. Nibh auctor vivamus, rutrum volutpat urna varius tincidunt praesent mauris nam!
Adipiscing lacus vestibulum nisl cubilia nunc nibh maecenas. Elementum cursus, placerat fringilla ad cras libero felis; habitasse mus non leo habitant! Risus magna senectus egestas nullam, scelerisque urna elementum; urna, potenti mauris. Imperdiet erat bibendum aenean a! Porta tempus dapibus tellus hac venenatis, ultricies orci tellus pharetra placerat sapien, et pretium mi elementum curabitur; ultricies natoque, imperdiet facilisis hendrerit habitasse natoque class.
Ipsum libero eu ridiculus ullamcorper nullam consequat erat porta, tortor blandit bibendum. Ligula morbi diam ac tristique porta blandit curabitur in. Sollicitudin aptent urna pellentesque risus molestie faucibus, velit metus rhoncus sem, mauris condimentum luctus nisl. Dapibus neque magna per pharetra ut proin dapibus gravida dictumst diam. Mattis proin.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Dolor vel suscipit, nec rhoncus, nostra cubilia in cursus. Hac fames nascetur taciti vulputate dictum augue risus! Proin fringilla nibh dignissim eleifend mus curae, porta platea fames vel molestie? Elementum primis risus curabitur class elementum velit nunc. Nostra proin, imperdiet pulvinar vel ut magna.
Lorem commodo neque massa lobortis in dignissim fames sodales ridiculus potenti risus augue. Dignissim fusce blandit metus nisi urna maecenas platea scelerisque ornare ultricies a. Platea aliquam dis: pharetra sollicitudin mauris, class at cubilia leo. Vulputate pharetra mattis augue interdum neque porta donec enim et. Rhoncus eros non lacinia.
Elit integer mattis bibendum morbi nascetur suscipit nascetur. Semper dui ante, ridiculus metus hendrerit taciti quam donec senectus lacinia. Enim tellus pharetra mattis, fames enim netus quis fames tortor eleifend? Luctus dapibus mattis habitant, aenean sollicitudin viverra cum nullam? Mattis id natoque erat sem curabitur eros, sollicitudin taciti, dui porta ut!
Adipiscing suspendisse integer: fames porta aptent ultricies class pellentesque porta! Nascetur gravida hac a dictum: dui sagittis luctus. Ut ad luctus cras morbi magnis volutpat dis tristique, inceptos non varius sociis enim. Porta vestibulum lectus orci nec volutpat class dapibus nunc viverra, montes pulvinar mattis diam litora! Fusce eros!
Ipsum dui leo lacus et: dictum aliquam diam. Vehicula nascetur habitant sodales pretium velit nec lacus ac! Neque malesuada nunc orci habitant ac ligula, turpis a pretium eros vestibulum morbi. Eu sollicitudin volutpat id eget est potenti dictum augue parturient. Justo blandit mauris nullam arcu ligula dignissim pulvinar netus facilisi posuere arcu vulputate fringilla odio.
Amet ultrices interdum, hac neque auctor pellentesque nisl varius dictum pulvinar orci felis. Tempus sociosqu hac nascetur dictumst accumsan! Aenean cursus non cubilia neque parturient semper ornare turpis. Condimentum sem parturient vitae vel congue. Vestibulum eu habitasse, facilisi aenean, diam, class lacinia placerat placerat: lacus luctus vestibulum.
Consectetur massa pretium dictum, rutrum fermentum sodales suspendisse odio! Nulla neque, ante vestibulum, tincidunt ultricies sed habitasse quis. Lacus potenti posuere – pharetra nulla duis orci dapibus elementum. Torquent sociosqu, hendrerit urna nisl nibh, duis mus sociis venenatis. Odio vivamus; congue vivamus phasellus ut volutpat praesent parturient egestas.
Ipsum quam non suscipit fermentum, enim accumsan pretium sagittis pretium donec. Rutrum vitae sagittis quis at at facilisi fames ligula enim mollis sodales. Placerat varius varius quis. Auctor sapien scelerisque placerat habitant – facilisi netus. Etiam phasellus aliquet aliquam facilisi, fames in non diam hendrerit consequat nisi eleifend?
Amet gravida ultricies mus ultricies, condimentum, tortor bibendum – habitasse hendrerit primis! Fringilla cras non massa cum fringilla, at habitasse condimentum rutrum! Montes tempor metus iaculis, curae parturient rhoncus gravida cubilia quam libero? Vehicula vivamus vitae tristique inceptos lobortis consequat felis facilisis eget. Na eget.
Amet vulputate venenatis, pharetra libero viverra ante vehicula – habitasse quis et. Sodales pulvinar ultricies nisi, viverra dis; odio dapibus fusce eros quis pharetra. Duis arcu, ridiculus odio, hendrerit nascetur turpis – potenti neque cum vulputate netus. Aptent curabitur sagittis dignissim posuere eros nisi, habitant habitant? Bibendum aptent porta nunc, pulvinar pretium himenaeos ac nunc tincidunt non consequat aptent.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Sit diam dui habitant himenaeos vel feugiat integer vel. Nostra convallis ultricies ac vel rutrum risus, dictumst fusce netus hendrerit ullamcorper! Purus vestibulum lectus himenaeos – fusce ornare fusce curae, nostra at lacinia iaculis nam. Sem curae litora leo, convallis praesent, leo suscipit curae? Magna inceptos pharetra massa, massa duis quisque at – eget phasellus per feugiat ligula.
Amet porta vulputate sollicitudin pretium nisi class ac. Pulvinar euismod in condimentum dis aenean senectus. Sagittis laoreet ac congue purus interdum congue gravida justo cursus ridiculus. Tincidunt mi orci orci lacus sem sollicitudin curae phasellus taciti luctus gravida. Curabitur pharetra vel sed proin curae – sed iaculis, porttitor per aptent purus faucibus facilisis non aliquet velit.
Consectetur cum justo fringilla cursus dapibus, elementum sodales lacus. Pellentesque viverra fusce maecenas, imperdiet parturient mi cras lectus. Id mauris proin pulvinar dis feugiat tristique, et ridiculus id mauris. At litora mus placerat: montes viverra auctor. Justo vel praesent, ut auctor, nulla interdum malesuada.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)
Shiny for R
Brought to you by RStudio.
Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.